Hi Patrick, Are you able to reach out to Airbnb and tell them the situation to see what they can do to cancel it for you and also find another place for your guest.
I did that with a guest who continuously sent me emails a week before they were coming telling me things they required from tea upon arrival at midnight to cooking all night and making a full breakfast in the morning. Airbnb graciously found them other arrangements and cancelled with no effect to me. Good luck